Power transformer shield for radio receiver



Nov. 4, 1958 E D 2,859,337

POWER TRANSFORMER SHIELD FOR RADIO RECEIVER Filed March 15, 1954 IN VENTOR JAN JOO ST RIETVELD AGENT United States Patent POWER TRANSFORMERSHIELD FOR RADIO RECEIVER Jan Joost Rietveld, Eindhoven, Netherlands,assignor, by

mesue assignments, to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware The present invention relates to radioreceiving apparatus. More particularly, the invention relates to a radioreceiving apparatus comprising a frame aerial structurally united withthe apparatus, more particularly, an incorporated aerial. The componentparts of a radio receiver are, in general, housed in a rectangularcabinet of wood or other insulating material. It is often desired tounite the aerial, in the form of a frame, directly with the apparatus.For this purpose the frame is preferably arranged inside the cabinet ina vertical diagonal plane in order to obtain a maximum surface. Since inthis case the directional effect of the frame frequently gives rise tointerference, use is often made of two frame aerials each arranged in adifferent diagonal plane. These aerials are used separately or inconjunction, for example, in series combination, for the reception.

A receiver comprising such an aerial, which is structurally united withthe apparatus, provides the best results, if it is fed directly from thepower supply, for example, an alternating-current power source or adirectcurrent power source via a rectifier. Feeding by means of a supplytransformer gives rise to interference which is suppressed only withdifiiculty by electro-statically shielding the windings.

The invention has for its object to suppress this interference in asimple manner.

It must be assumed that the said interference is due to magneticcouplings between the frame and the windings of the supply transformerand that across these windings, parts of which may function ashigh-frequency resonant circuits, undue high-frequency currents mayoccur, producing interference in the reception.

The invention consists in that use is made of a supply transformerprovided with a magnetic shield. This shield may comprise a closedwinding of one or more turns, completely surrounding the transformer.The plane of the winding is parallel to the plane of the turns of thetransformer windings. The shield is preferably constructed in the formof an electrically closed tape surrounding the transformer at the areaof the windings.

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawing, wherein:

Fig. 1 is a schematic diagram of an embodiment of radio receivingapparatus viewed from the rear;

Fig. 2 is a schematic diagram of the transformer 6, 7 of the embodimentof Fig. I, viewed from the top; and

Fig. 3 is a schematic diagram of the transformer 6, 7 of the embodimentof Fig. 1, viewed from the rear.

Referring to Fig. 1, reference numeral 1 designates 2,859,337.- PatentedNov. 4, 1958 the cabinet of the receiving apparatus, made of wood orother insulating material. In the interior of the cabinet, in verticaldiagonal planes, provision is made of two frame windings 2 and 3, eachof which comprises one or more turns and which operate as receivingaerials. These windings may be included separately or in conjunction inthe input circuit of the first tube of the receiver. The cabinetcomprises, moreover, a chassis 4, in which and on which the variousparts of the apparatus, for example, the tubes 5, are mounted.

It is assumed that the receiver is fed from an alternating-current powersource and that provision is made of a supply transformer, constructedin this case as a shell transformer, the central core of which supportsthe windings. The magnetic circuit 6 of the transformer is, as usual,laminated, and the windings 7 of the transformer are arranged coaxiallyabout the central core. It has been found to be difiicult to arrange thetransformer in a manner such that it does not produce interference.

According to the invention, a magnetic shield in the form of a closedtape 8 is provided to surround the entire transformer, i. e. thewindings and the cores. The tape 8 may be made of material of goodconductivity, preferably of copper and the ends may be united bysoldering at 9 in a manner such that an electrically good conductingcircuit is formed. The width of the tape may be equal to the length ofthe coil or it may be smaller.

It has been found that the said undue magnetic couplings may thus besuppressed to such an extent that substantially no interference occurs.

The frame aerial or aerials may, as an alternative, be arranged in adifferent manner in or on the cabinet.

While the invention has been described by means of a specific exampleand in a specific embodiment; I do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

A radio receiver comprising a radio signal processing assembly includingan alternating current supply transformer for energizing said signalprocessing assembly and a frame aerial comprising a plurality of turnsof conductive material arranged in a plurality of given planes andstructurally united with said assembly and in close proximity thereto,said supply transformer comprising a plurality of windings positionedsubstantially within said turns and having a common axis and a magneticshielding member comprising a closed winding of copper tape looped overthe windings of said transformer and interposed between the saidwindings of said transformer and said aerial, said closed winding oftape being arranged with its axis substantially perpendicular to saidplanes.

References Cited in the file of this patent UNITED STATES PATENTS1,775,276 Ferguson et al. Sept. 9, 1930 2,228,174 Miller Ian. 7, 19412,388,848 Howe Nov. 13, 1945 2,515,333 Buflington' July 18, 19502,520,984 Williams et al. Sept. 5, 1950 2,552,816 Root May 15, 1951

